Molecular genetic advances in tuberous sclerosis

Paradigm shift in the treatment of tuberous sclerosis: Effectiveness of everolimus

Tuberous sclerosis complex (TSC) is an autosomal dominant disease characterised by abnormal cell proliferation and differentiation that affects multiple organs and can lead to the growth of hamartomas. Tuberous sclerosis complex is caused by the disinhibition of the protein mTOR (mammalian target of rapamycin). In the past, various therapeutic approaches, even if only symptomatic, have been attempted to improve the clinical effects of this disease. While all of these therapeutic strategies are useful and are still used and indicated, they are symptomatic therapies based on the individual symptoms of the disease and therefore not fully effective in modifying long-term outcomes. A new therapeutic approach is the introduction of allosteric inhibitors of mTORC1, which allow restoration of metabolic homeostasis in mutant cells, potentially eliminating most of the clinical manifestations associated with Tuberous sclerosis complex. Everolimus, a mammalian target of the rapamycin inhibitor, is able to reduce hamartomas, correcting the specific molecular defect that causes Tuberous sclerosis complex. In this review, we report the findings from the literature on the use of everolimus as an effective and safe drug in the treatment of TSC manifestations affecting various organs, from the central nervous system to the heart.

Recent Advances in Renal Tumors with TSC/mTOR Pathway Abnormalities in Patients with Tuberous Sclerosis Complex and in the Sporadic Setting

A spectrum of renal tumors associated with frequent TSC/mTOR (tuberous sclerosis complex/mechanistic target of rapamycin) pathway gene alterations (in both the germline and sporadic settings) have recently been described. These include renal cell carcinoma with fibromyomatous stroma (RCC FMS), eosinophilic solid and cystic renal cell carcinoma (ESC RCC), eosinophilic vacuolated tumor (EVT), and low-grade oncocytic tumor (LOT). Most of these entities have characteristic morphologic and immunohistochemical features that enable their recognition without the need for molecular studies. In this report, we summarize recent advances and discuss their evolving complexity.

Rapamycin and rapalogs for tuberous sclerosis complex

BACKGROUND

Potential benefits of rapamycin or rapalogs for treating people with tuberous sclerosis complex (TSC) have been shown. Currently everolimus (a rapalog) is only approved for TSC-associated renal angiomyolipoma and subependymal giant cell astrocytoma (SEGA), but not other manifestations of TSC. A systematic review needs to establish evidence for rapamycin or rapalogs for various manifestations in TSC. This is an updated review.

OBJECTIVES

To determine the effectiveness of rapamycin or rapalogs in people with TSC for decreasing tumour size and other manifestations and to assess the safety of rapamycin or rapalogs in relation to their adverse effects.

SEARCH METHODS

We identified relevant studies from the Cochrane-Central-Register-of-Controlled-Trials (CENTRAL), Ovid MEDLINE and ongoing trials registries with no language restrictions. We searched conference proceedings and abstract books of conferences. Date of the last searches: 15 July 2022.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs of rapamycin or rapalogs in people with TSC.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias of each study; a third review author verified the extracted data and risk of bias decisions. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

The current update added seven RCTs, bringing the total number to 10 RCTs (with 1008 participants aged 3 months to 65 years; 484 males). All TSC diagnoses were by consensus criteria as a minimum. In parallel studies, 645 participants received active interventions and 340 placebo. Evidence is low-to-high certainty and study quality is mixed; mostly a low risk of bias across domains, but one study had a high risk of performance bias (lack of blinding) and three studies had a high risk of attrition bias. Manufacturers of the investigational products supported eight studies. Systemic administration Six studies (703 participants) administered everolimus (rapalog) orally. More participants in the intervention arm reduced renal angiomyolipoma size by 50% (risk ratio (RR) 24.69, 95% confidence interval (CI) 3.51 to 173.41; P = 0.001; 2 studies, 162 participants, high-certainty evidence). In the intervention arm, more participants in the intervention arm reduced SEGA tumour size by 50% (RR 27.85, 95% CI 1.74 to 444.82; P = 0.02; 1 study; 117 participants; moderate-certainty evidence) ,and reported more skin responses (RR 5.78, 95% CI 2.30 to 14.52; P = 0.0002; 2 studies; 224 participants; high-certainty evidence). In one 18-week study (366 participants), the intervention led to 25% fewer seizures (RR 1.63, 95% CI 1.27 to 2.09; P = 0.0001) or 50% fewer seizures (RR 2.28, 95% CI 1.44 to 3.60; P = 0.0004); but there was no difference in numbers being seizure-free (RR 5.30, 95% CI 0.69 to 40.57; P = 0.11) (moderate-certainty evidence). One study (42 participants) showed no difference in neurocognitive, neuropsychiatry, behavioural, sensory and motor development (low-certainty evidence). Total adverse events (AEs) did not differ between groups (RR 1.09, 95% CI 0.97 to 1.22; P = 0.16; 5 studies; 680 participants; high-certainty evidence). However, the intervention group experienced more AEs resulting in withdrawal, interruption of treatment, or reduced dose (RR 2.61, 95% CI 1.58 to 4.33; P = 0.0002; 4 studies; 633 participants; high-certainty evidence and also reported more severe AEs (RR 2.35, 95% CI 0.99 to 5.58; P = 0.05; 2 studies; 413 participants; high-certainty evidence). Topical (skin) administration Four studies (305 participants) administered rapamycin topically. More participants in the intervention arm showed a response to skin lesions (RR 2.72, 95% CI 1.76 to 4.18; P < 0.00001; 2 studies; 187 participants; high-certainty evidence) and more participants in the placebo arm reported a deterioration of skin lesions (RR 0.27, 95% CI 0.15 to 0.49; 1 study; 164 participants; high-certainty evidence). More participants in the intervention arm responded to facial angiofibroma at one to three months (RR 28.74, 95% CI 1.78 to 463.19; P = 0.02) and three to six months (RR 39.39, 95% CI 2.48 to 626.00; P = 0.009; low-certainty evidence). Similar results were noted for cephalic plaques at one to three months (RR 10.93, 95% CI 0.64 to 186.08; P = 0.10) and three to six months (RR 7.38, 95% CI 1.01 to 53.83; P = 0.05; low-certainty evidence). More participants on placebo showed a deterioration of skin lesions (RR 0.27, 95% CI 0.15 to 0.49; P < 0.0001; 1 study; 164 participants; moderate-certainty evidence). The intervention arm reported a higher general improvement score (MD -1.01, 95% CI -1.68 to -0.34; P < 0.0001), but no difference specifically in the adult subgroup (MD -0.75, 95% CI -1.58 to 0.08; P = 0.08; 1 study; 36 participants; moderate-certainty evidence). Participants in the intervention arm reported higher satisfaction than with placebo (MD -0.92, 95% CI -1.79 to -0.05; P = 0.04; 1 study; 36 participants; low-certainty evidence), although again with no difference among adults (MD -0.25, 95% CI -1.52 to 1.02; P = 0.70; 1 study; 18 participants; low-certainty evidence). Groups did not differ in change in quality of life at six months (MD 0.30, 95% CI -1.01 to 1.61; P = 0.65; 1 study; 62 participants; low-certainty evidence). Treatment led to a higher risk of any AE compared to placebo (RR 1.72, 95% CI 1.10, 2.67; P = 0.02; 3 studies; 277 participants; moderate-certainty evidence); but no difference between groups in severe AEs (RR 0.78, 95% CI 0.19 to 3.15; P = 0.73; 1 study; 179 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Oral everolimus reduces the size of SEGA and renal angiomyolipoma by 50%, reduces seizure frequency by 25% and 50% and implements beneficial effects on skin lesions with no difference in the total number of AEs compared to placebo; however, more participants in the treatment group required a dose reduction, interruption or withdrawal and marginally more experienced serious AEs compared to placebo. Topical rapamycin increases the response to skin lesions and facial angiofibroma, an improvement score, satisfaction and the risk of any AE, but not severe adverse events. With caution regarding the risk of severe AEs, this review supports oral everolimus for renal angiomyolipoma, SEGA, seizure, and skin lesions, and topical rapamycin for facial angiofibroma.

Sorafenib inhibits invasion of multicellular organoids that mimic Lymphangioleiomyomatosis nodules

Lymphangioleiomyomatosis (LAM) is a debilitating, progressive lung disease with few therapeutic options, largely due to a paucity of mechanistic knowledge of disease pathogenesis. Lymphatic endothelial cells (LECs) are known to envelope and invade clusters of LAM-cells, comprising of smooth muscle α-actin and/or HMB-45 positive "smooth muscle-like cells" however the role of LECs in LAM pathogenesis is still unknown. To address this critical knowledge gap, we investigated wether LECs interact with LAM-cells to augment their metastatic behaviour of LAM-cells. We performed in situ spatialomics and identified a core of transcriptomically related cells within the LAM nodules. Pathway analysis highlights wound and pulmonary healing, VEGF signaling, extracellular matrix/actin cytoskeletal regulating and the HOTAIR regulatory pathway enriched in the LAM Core cells. We developed an organoid co-culture model combining primary LAM-cells with LECs and applied this to evaluate invasion, migration, and the impact of Sorafenib, a multi-kinase inhibitor. LAM-LEC organoids had significantly higher extracellular matrix invasion, decreased solidity and a greater perimeter, reflecting increased invasion compared to non-LAM control smooth muscle cells. Sorafenib significantly inhibited this invasion in both LAM spheroids and LAM-LEC organoids compared to their respective controls. We identified TGFβ1ι1, a molecular adapter coordinating protein-protein interactions at the focal adhesion complex and known to regulate VEGF, TGFβ and Wnt signalling, as a Sorafenib-regulated kinase in LAM-cells. In conclusion we have developed a novel 3D co-culture LAM model and have demonstrated the effectiveness of Sorafenib to inhibit LAM-cell invasion, identifying new avenues for therapeutic intervention.

Kinase Inhibitors in Genetic Diseases

Over the years, several studies have shown that kinase-regulated signaling pathways are involved in the development of rare genetic diseases. The study of the mechanisms underlying the onset of these diseases has opened a possible way for the development of targeted therapies using particular kinase inhibitors. Some of these are currently used to treat other diseases, such as cancer. This review aims to describe the possibilities of using kinase inhibitors in genetic pathologies such as tuberous sclerosis, RASopathies, and ciliopathies, describing the various pathways involved and the possible targets already identified or currently under study.

Genetics, Genomics and Emerging Molecular Therapies of Pancreatic Cancer

The number of cases of pancreatic cancers in 2019 in Poland was 3852 (approx. 2% of all cancers). The course of the disease is very fast, and the average survival time from the diagnosis is 6 months. Only <2% of patients live for 5 years from the diagnosis, 8% live for 2 years, and almost half live for only about 3 months. A family predisposition to pancreatic cancer occurs in about 10% of cases. Several oncogenes in which somatic changes lead to the development of tumours, including genes BRCA1/2 and PALB2, TP53, CDKN2A, SMAD4, MLL3, TGFBR2, ARID1A and SF3B1, are involved in pancreatic cancer. Between 4% and 10% of individuals with pancreatic cancer will have a mutation in one of these genes. Six percent of patients with pancreatic cancer have NTRK pathogenic fusion. The pathogenesis of pancreatic cancer can in many cases be characterised by homologous recombination deficiency (HRD)-cell inability to effectively repair DNA. It is estimated that from 24% to as many as 44% of pancreatic cancers show HRD. The most common cause of HRD are inactivating mutations in the genes regulating this DNA repair system, mainly BRCA1 and BRCA2, but also PALB2, RAD51C and several dozen others.

Spine morphogenesis and synapse formation in tubular sclerosis complex models

Tuberous sclerosis complex (TSC) is caused by mutations in the Tsc1 or Tsc2 genes, whose products form a complex and inactivate the small G-protein Rheb1. The activation of Rheb1 may cause refractory epilepsy, intellectual disability, and autism, which are the major neuropsychiatric manifestations of TSC. Abnormalities in dendritic spines and altered synaptic structure are hallmarks of epilepsy, intellectual disability, and autism. In addition, spine dysmorphology and aberrant synapse formation are observed in TSC animal models. Therefore, it is important to investigate the molecular mechanism underlying the regulation of spine morphology and synapse formation in neurons to identify therapeutic targets for TSC. In this review, we focus on the representative proteins regulated by Rheb1 activity, mTORC1 and syntenin, which are pivotal downstream factors of Rheb1 in the alteration of spine formation and synapse function in TSC neurons.

ETV2 regulates PARP-1 binding protein to induce ER stress-mediated death in tuberin-deficient cells

Lymphangioleiomyomatosis (LAM) is a rare progressive disease, characterized by mutations in the tuberous sclerosis complex genes (TSC1 or TSC2) and hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1). Here, we report that E26 transformation-specific (ETS) variant transcription factor 2 (ETV2) is a critical regulator of Tsc2-deficient cell survival. ETV2 nuclear localization in Tsc2-deficient cells is mTORC1-independent and is enhanced by spleen tyrosine kinase (Syk) inhibition. In the nucleus, ETV2 transcriptionally regulates poly(ADP-ribose) polymerase 1 binding protein (PARPBP) mRNA and protein expression, partially reversing the observed down-regulation of PARPBP expression induced by mTORC1 blockade during treatment with both Syk and mTORC1 inhibitors. In addition, silencing Etv2 or Parpbp in Tsc2-deficient cells induced ER stress and increased cell death in vitro and in vivo. We also found ETV2 expression in human cells with loss of heterozygosity for TSC2, lending support to the translational relevance of our findings. In conclusion, we report a novel ETV2 signaling axis unique to Syk inhibition that promotes a cytocidal response in Tsc2-deficient cells and therefore maybe a potential alternative therapeutic target in LAM.

Cortical Dysplasia and the mTOR Pathway: How the Study of Human Brain Tissue Has Led to Insights into Epileptogenesis

Type II focal cortical dysplasia (FCD) is a neuropathological entity characterised by cortical dyslamination with the presence of dysmorphic neurons only (FCDIIA) or the presence of both dysmorphic neurons and balloon cells (FCDIIB). The year 2021 marks the 50th anniversary of the recognition of FCD as a cause of drug resistant epilepsy, and it is now the most common reason for epilepsy surgery. The causes of FCD remained unknown until relatively recently. The study of resected human FCD tissue using novel genomic technologies has led to remarkable advances in understanding the genetic basis of FCD. Mechanistic parallels have emerged between these non-neoplastic lesions and neoplastic disorders of cell growth and differentiation, especially through perturbations of the mammalian target of rapamycin (mTOR) signalling pathway. This narrative review presents the advances through which the aetiology of FCDII has been elucidated in chronological order, from recognition of an association between FCD and the mTOR pathway to the identification of somatic mosaicism within FCD tissue. We discuss the role of a two-hit mechanism, highlight current challenges and future directions in detecting somatic mosaicism in brain and discuss how knowledge of FCD may inform novel precision treatments of these focal epileptogenic malformations of human cortical development.

Beyond Protein Synthesis; The Multifaceted Roles of Tuberin in Cell Cycle Regulation

The ability of cells to sense diverse environmental signals, including nutrient availability and conditions of stress, is critical for both prokaryotes and eukaryotes to mount an appropriate physiological response. While there is a great deal known about the different biochemical pathways that can detect and relay information from the environment, how these signals are integrated to control progression through the cell cycle is still an expanding area of research. Over the past three decades the proteins Tuberin, Hamartin and TBC1D7 have emerged as a large protein complex called the Tuberous Sclerosis Complex. This complex can integrate a wide variety of environmental signals to control a host of cell biology events including protein synthesis, cell cycle, protein transport, cell adhesion, autophagy, and cell growth. Worldwide efforts have revealed many molecular pathways which alter Tuberin post-translationally to convey messages to these important pathways, with most of the focus being on the regulation over protein synthesis. Herein we review the literature supporting that the Tuberous Sclerosis Complex plays a critical role in integrating environmental signals with the core cell cycle machinery.

Identification of a Novel Canonical Splice Site Variant TSC2 c.2967-1G>T That is Not Associated With Tuberous Sclerosis Pathogenesis

Tuberous sclerosis, also known as tuberous sclerosis complex (TSC), is an autosomal dominant defect characterized by hamartomas in multiple organ systems. Inactivating variants cause this defect in either the TSC1 gene or the TSC2 gene, leading to hamartin or tuberin protein dysfunction, thus resulting in TSC. The diagnostic criteria for TSC suggest that it can be diagnosed by identifying a heterozygous pathogenic variant of TSC1 or TSC2, even in the absence of clinical signs. In a 4-year-old girl, we identified a splicing variant (NM_000548.4: c.2967-1G>T) that she inherited from her father. Neither the girl (patient) nor her father showed typical features of TSC. This variant is located in a NAGNAG acceptor, which can produce mRNA isoforms that differ by a three-nucleotide indel. Reverse transcription polymerase chain reaction analysis of the patient and both parents' blood RNA samples suggested two different splicing patterns, and these two splicing patterns differed in the presence or absence of the first codon of exon 27, thus providing two splicing products designated as isoforms A and B, respectively. Furthermore, the proportions of these two patterns varied between the patient and either parent. A minigene assay further confirmed that the c.2967-1G>T variant led to the absence of isoform A (including the first codon of exon 27). The finding of our study demonstrates this variant, c.2967-1G>T, disrupts the balance of an alternative splice event which involves the use of two tandem alternatives acceptors and is not associated with typical symptoms of tuberous sclerosis. Our finding is of importance for genetic counseling and suggests that we need to be vigilant to avoid misdiagnosis when we encounter such a site.

Revisiting Brain Tuberous Sclerosis Complex in Rat and Human: Shared Molecular and Cellular Pathology Leads to Distinct Neurophysiological and Behavioral Phenotypes

Tuberous sclerosis complex (TSC) is a dominant autosomal genetic disorder caused by loss-of-function mutations in TSC1 and TSC2, which lead to constitutive activation of the mammalian target of rapamycin C1 (mTORC1) with its decoupling from regulatory inputs. Because mTORC1 integrates an array of molecular signals controlling protein synthesis and energy metabolism, its unrestrained activation inflates cell growth and division, resulting in the development of benign tumors in the brain and other organs. In humans, brain malformations typically manifest through a range of neuropsychiatric symptoms, among which mental retardation, intellectual disabilities with signs of autism, and refractory seizures, which are the most prominent. TSC in the rat brain presents the first-rate approximation of cellular and molecular pathology of the human brain, showing many instructive characteristics. Nevertheless, the developmental profile and distribution of lesions in the rat brain, with neurophysiological and behavioral manifestation, deviate considerably from humans, raising numerous research and translational questions. In this study, we revisit brain TSC in human and Eker rats to relate their histopathological, electrophysiological, and neurobehavioral characteristics. We discuss shared and distinct aspects of the pathology and consider factors contributing to phenotypic discrepancies. Given the shared genetic cause and molecular pathology, phenotypic deviations suggest an incomplete understanding of the disease. Narrowing the knowledge gap in the future should not only improve the characterization of the TSC rat model but also explain considerable variability in the clinical manifestation of the disease in humans.

Genetics of tuberous sclerosis complex: an update

PURPOSE

To review the current genetic aspects of tuberous sclerosis complex.

METHODS

Review of the literature.

RESULTS

Tuberous sclerosis complex (TSC), a long known childhood-onset monogenic disorder, characterized by hamartoma formation affecting mainly the brain, heart, kidney, lung, and skin, is associated with a high morbidity burden and risk of a reduced life span. The identification of TSC1 and TSC2, as tumor suppressor genes causative of the disorder, led to the elucidation of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway and its pivotal role in the pathogenesis of hamartoma formation. This knowledge was translated into standard clinical practice with the discovery of rapamycin, and additional analogues, as inhibitors of mTORC1.

CONCLUSION

Next-generation sequencing was proven to be fundamental to drive research of tumorigenesis in TSC, hopefully leading to new therapeutic options in the future.

Prevalence, mortality and healthcare economic burden of tuberous sclerosis in Hong Kong: a population-based retrospective cohort study (1995-2018)

Background

We aim to elucidate the disease impact by accounting the prevalence, survival rate, genetics, mTOR inhibitor use and direct costs of tuberous sclerosis complex (TSC) in our local setting. TSC patients with documented visits to our local public hospitals in 1995–2018 were identified. The public hospitals captured most if not all local TSC patients. Demographics such as age, sex, death, genetic profiles were retrieved from the central electronic database. Data including prevalence, age distribution and survival rate were analysed. Direct cost was calculated with reference to the drug use and number of visits to various public hospital facilities.

Results

We identified 284 surviving TSC patients (55.3% male) in Hong Kong. The age range was from 4.5 months to 89.9 years, with a median age of 27.2 years. Paediatrics (< 18 years) to adult (≥18 years) ratio was 1:2.84. The overall prevalence of TSC patients was 3.87 in 100,000 (i.e. 1 in 25,833). Genetically, TSC1:TSC2 ratio is 1:2.7.

Thirty seven patients died within the study period. The age of death ranged from 7.6 years to 77.8 years, with a median age of death at 36.6 years (IQR: 24.7–51.1 years). Most patients survived till adulthood. Survival rate at 20 and 50 years follow-up was 98.6 and 79.5% respectively.

Two hundred and twenty nine TSC patients (71.3%) had neurological manifestations, sixteen patients (5.0%) had chronic kidney diseases and five patients (1.6%) had pulmonary lymphangioleiomyomatosis. Forty seven (16.5%) TSC patients were prescribed with mTOR inhibitors within the study period. Healthcare facility utilization was further analysed in the 2008–2018 cohort. In particular, the mean number of specialist out-patient clinic visits per patient-year was 9.23 per patient-year, which was 4.91 times more than that of local general population.

Conclusions

Prevalence of local TSC patients is within the range of that reported in the literature. Local TSC patients have fair long term survival, but they require disproportionally high healthcare cost when compared with the general population, particularly in terms of outpatient (OP) visits. Although effective disease-modifying agent (i.e. mTOR inhibitor) is available, it was not widely used yet in Hong Kong despite the fact that Government approved and supported its use recently. Further research on quality of life and setting up a comprehensive patient registry are necessary for more accurate assessment of cost and benefit.

Fetal cardiac rhabdomyoma due to paternal mosaicism of TSC2: A case report

RATIONALE

Rhabdomyoma is the most common type of fetal heart tumors and 50% to 60% of cardiac rhabdomyomas are associated with tuberous sclerosis complex (TSC). TSC is characterized by hamartomas in multiple organ systems including the brain, heart, skin, lungs, and kidneys, resulting in complications such as learning difficulties, epilepsy, behavioral problems, and renal failure. The etiological diagnosis of Rhabdomyoma is very important.

PATIENT CONCERNS

A 22-year-old G2P0 woman chose to terminate the pregnancy at 24 + 4 weeks of gestation because of the presence of a cardiac space-occupying lesion in the fetus.

DIAGNOSES

The pathological diagnosis of cardiac neoplasm tissue was cardiac rhabdomyoma, but the etiology was unknown.

INTERVENTIONS

Targeted exome capture, next-generation sequencing (NGS) and sanger sequencing were performed on peripheral blood lymphocytes and paternal sperm.

OUTCOMES

Targeted exome capture sequencing revealed a novel heterozygous variant (NM_000548, c.2294delC) in the tuberous sclerosis 2 (TSC2) gene. Sanger sequencing of maternal blood samples showed no mutation at this locus, however, suspected low level mosaicism was observed in paternal blood samples. Deep NGS analysis showed that about 7% paternal alleles from peripheral blood leucocytes and 20% paternal alleles from sperm carried the mutation consistent with somatic and germinal mosaicism.

LESSONS

For fetuses suspected of TSC, when pathogenic mutations are detected in the tuberous sclerosis 1 (TSC1) or TSC2 gene, it is recommended that the parents should be screened by deep NGS and their germ cells are screened as well if necessary, which would help to predict the risk of TSC recurrence in the next pregnancy.

Renal Manifestations of Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is a genetic condition caused by a mutation in either the TSC1 or TSC2 gene. Disruption of either of these genes leads to impaired production of hamartin or tuberin proteins, leading to the manifestation of skin lesions, tumors, and seizures. TSC can manifest in multiple organ systems with the cutaneous and renal systems being the most commonly affected. These manifestations can secondarily lead to the development of hypertension, chronic kidney disease, and neurocognitive declines. The renal pathologies most commonly seen in TSC are angiomyolipoma, renal cysts, and less commonly, oncocytomas. In this review, we highlight the current understanding on the renal manifestations of TSC along with current diagnosis and treatment guidelines.

Genotype and Phenotype Analysis of Chinese Children With Tuberous Sclerosis Complex: A Pediatric Cohort Study

Tuberous sclerosis complex (TSC) is a genetic condition characterized by the occurrence of hamartomatous wounds stemming from the dysfunction of the mammalian target of rapamycin (mTOR) pathway. We investigated the clinical phenotypes and genetic variants in 243 unrelated probands and their families in China. Exome sequencing, targeted sequencing or multiplex ligation-dependent probe amplification (MLPA) was performed in 174 children with TSC, among whom 31 (17.82%) patients/families were identified as having pathogenic or likely pathogenic variants in the TSC1 gene, 120 (68.97%) as having pathogenic or likely pathogenic variants in the TSC2 gene and 23 (13.21%) as having no pathogenic or likely pathogenic variants identified (NMI). In the 31 patients with pathogenic or likely pathogenic TSC1 variants, 10 novel variants were detected among 26 different variants. In all 120 patients with TSC2 variants, 39 novel variants were found among a total of 107 different variants. We compared the phenotypes of the individuals with TSC1 pathogenic variants, TSC2 pathogenic variants and NMI. Patients with TSC2 variants were first diagnosed at a younger age (p = 0.003) and had more retinal hamartomas (p = 0.003) and facial angiofibromas (p = 0.027) (age ≥ 3 years) than individuals with TSC1 variants. Compared with individuals with TSC1/TSC2 pathogenic variants, NMI individuals had fewer cortical tubers (p = 0.003). Compared with individuals with TSC1 pathogenic variants, NMI patients had more retinal hamartomas (p = 0.035), and compared with individuals with TSC2 pathogenic variants, they had less epilepsy (p = 0.003) and fewer subependymal nodules (SENs) (p = 0.004).

Rapamycin-upregulated miR-29b promotes mTORC1-hyperactive cell growth in TSC2-deficient cells by downregulating tumor suppressor retinoic acid receptor β (RARβ)

miR-29b has been identified as a rapamycin-induced microRNA (miRNA) in Tsc2-deficient, mTORC1-hyperactive cells. The biological significance of this induction of miR-29b is unknown. We have found that miR-29b acts as an oncogenic miRNA in Tsc2-deficient cells: inhibition of miR-29b suppressed cell proliferation, anchorage-independent cell growth, cell migration, invasion, and the growth of Tsc2-deficient tumors in vivo. Importantly, the combination of miR-29b inhibition with rapamycin treatment further inhibited these tumor-associated cellular processes. To gain insight into the molecular mechanisms by which miR-29b promotes tumorigenesis, we used RNA sequencing to identify the tumor suppressor retinoid receptor beta (RARβ) as a target gene of miR-29b. We found that miR-29b directly targeted the 3'UTR of RARβ. Forced expression of RARβ reversed the effects of miR-29b overexpression in proliferation, migration, and invasion, indicating that it is a critical target. miR-29b expression correlated with low RARβ expression in renal clear cell carcinomas and bladder urothelial carcinomas, tumors associated with TSC gene mutations. We further identified growth family member 4 (ING4) as a novel interacting partner of RARβ. Overexpression of ING4 inhibited the migration and invasion of Tsc2-deficient cells while silencing of ING4 reversed the RARβ-mediated suppression of cell migration and invasion. Taken together, our findings reveal a novel miR-29b/RARβ/ING4 pathway that regulates tumorigenic properties of Tsc2-deficient cells, and that may serve as a potential therapeutic target for TSC, lymphangioleiomyomatosis (LAM), and other mTORC1-hyperactive tumors.

A novel de novo splicing mutation c.1444-2A>T in the TSC2 gene causes exon skipping and premature termination in a patient with tuberous sclerosis syndrome

Tuberous sclerosis complex (TSC) syndrome is a neurocutaneous syndrome that affects the brain, skin, and kidneys that has an adverse impact on the patient's health and quality of life. There have been several recent advances that elucidate the genetic complex of this disorder that will help understand the basic neurobiology of this disorder. We report a Tunisian patient with clinical manifestations of TSC syndrome. We investigated the causative molecular defect in this patient using PCR followed by direct sequencing. Subsequently, in silico studies and mRNA analysis were performed to study the pathogenicity of the new variation found in the TSC2. Bioinformatics tools predicted that the novel mutation c.1444-2A>T have pathogenic effects on splicing machinery. RT-PCR followed by sequencing revealed that the mutation c.1444-2A>T generates two aberrant transcripts. The first, with exon 15 skipping, is responsible for the loss of 52 amino acids, which causes the production of an aberrant protein isoform. The second, with the inclusion of 122 nucleotides of intron 14, is responsible for the creation of new premature termination codons (TGA), which causes the production of a truncated TSC2 protein. This study highlighted the clinical features of a Tunisian patient with TSC syndrome and revealed a splicing mutation c.1444-2A>T within intron 14 of TSC2 gene, which is present for the first time using Sanger sequencing approach, as a disease-causing mutation in a Tunisian patient with TSC syndrome.

Pancreatic Neuroendocrine Tumor in a Young Child With Tuberous Sclerosis Complex 1

Pancreatic neuroendocrine tumors (PNETs) occur in the context of tuberous sclerosis complex (TSC). To date, PNETs in association with TSC have been described almost exclusively in adults and in the context of TSC2. We present the evaluation of a PNET in a young child with TSC1. A 3-year, 6-month-old boy with TSC1 was found on surveillance to have a small pancreatic lesion measuring 0.4 cm on magnetic resonance imaging (MRI). The lesion showed interval enlargement to 1 cm on serial MRI studies during the ensuing 16 weeks. Endocrine laboratory tests did not reveal a functional tumor. The patient underwent enucleation of the pancreatic lesion. Microscopic examination defined a well-differentiated PNET, grade II/intermediate grade with a mitotic rate of two mitotic figures per 10 high-powered field and Ki-67 proliferation index of ∼15%. The tumor was positive for the TSC1 gene mutation. The patient was free of tumor recurrence at the 5-year follow-up examination, as determined by endocrine surveillance and annual MRI of the abdomen. In the reported data, PNET in patients with TSC has been primarily reported in association with TSC2. Our case demonstrates that patients with TSC1 can develop PNETs, even at an early age. The international TSC consensus group 2012 recommendation was to obtain MRI of the abdomen every 1 to 3 years for surveillance of renal angiomyolipomas and renal cystic disease. It might be beneficial to add a pancreatic protocol to the surveillance guidelines to evaluate for PNET.

Incidence of tuberous sclerosis and age at first diagnosis: new data and emerging trends from a national, prospective surveillance study

Background

Tuberous Sclerosis Complex (TSC) is a rare multisystem disorder. In 2012 diagnostic criteria for TSC were revised. However, data on the incidence of TSC are limited.

Methods

Prospective, national surveillance study in Germany over a 2-year-period (03/2015–02/2017) using current revised criteria for TSC. Patients up to the age of 18 years with a new diagnosis of definite or possible TSC (clinical and/or genetic) were included. The aims of this study were 1) to generate up-to-date data on the incidence of definite or possible TSC, 2) to assess age at first diagnosis, and 3) to compare these data with previous epidemiologic data.

Results

In total, 86 patients met inclusion criteria (definite or possible TSC) with a median age at diagnosis of 6 months (range: 5 months before birth – 197 months of age). Among patients identified with features of TSC, 73.3% met criteria for definite diagnosis (median age: 7 months) and 26.7% met criteria for a possible diagnosis (median age: 3 months). 55.8% of patients were male. When excluding prenatally diagnosed patients, median age at diagnosis was 11 months with a range of 0 to 197 months. The 3 most common clinical features at diagnosis of TSC were central nervous system involvement in 73.3% patients (of these 95.2% experienced seizures), cutaneous involvement in 58.1% patients (with the most common lesion being hypomelanotic macules in 92%) and cardiac rhabdomyoma in half of the patients. Cardiac rhabdomyoma were detected by prenatal ultrasonography in 22.1% of patients. The presence of cardiac rhabdomyoma was associated with cardiac arrhythmias in 25.6% (about 13% of all diagnosed patients) in our cohort. The overall prevalence of seizure disorders was 69.8%. The annual incidence rate of TSC is estimated at a minimum of 1:17.785 live births. However correcting for underreporting, the estimated incidence rate of definite or possible TSC is approximately 1:6.760–1:13.520 live births in Germany.

Conclusions

This is the first study that assessed prospectively the incidence rate of TSC in children and adolescents using the updated diagnostic criteria of 2012. This prospective surveillance study demonstrates a low age at first diagnosis (median: 6 months), likely due to antenatal detection of cardiac rhabdomyoma. Early diagnosis bears the potential for implementing effective therapies at an earlier stage.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0870-y) contains supplementary material, which is available to authorized users.

TSC2-deficient tumors have evidence of T cell exhaustion and respond to anti-PD-1/anti-CTLA-4 immunotherapy

Tuberous sclerosis complex (TSC) is an incurable multisystem disease characterized by mTORC1-hyperactive tumors. TSC1/2 mutations also occur in other neoplastic disorders, including lymphangioleiomyomatosis (LAM) and bladder cancer. Whether TSC-associated tumors will respond to immunotherapy is unknown. We report here that the programmed death 1 coinhibitory receptor (PD-1) is upregulated on T cells in renal angiomyolipomas (AML) and pulmonary lymphangioleiomyomatosis (LAM). In C57BL/6J mice injected with syngeneic TSC2-deficient cells, anti-PD-1 alone decreased 105K tumor growth by 67% (P < 0.0001); the combination of PD-1 and CTLA-4 blockade was even more effective in suppressing tumor growth. Anti-PD-1 induced complete rejection of TSC2-deficient 105K tumors in 37% of mice (P < 0.05). Double blockade of PD-1 and CTLA-4 induced rejection in 62% of mice (P < 0.01). TSC2 reexpression in TSC2-deficient TMKOC cells enhanced antitumor immunity by increasing T cell infiltration and production of IFN-γ/TNF-α by T cells, suggesting that TSC2 and mTORC1 play specific roles in the induction of antitumor immunity. Finally, 1 month of anti-PD-1 blockade reduced renal tumor burden by 53% (P < 0.01) in genetically engineered Tsc2+/- mice. Taken together, these data demonstrate for the first time to our knowledge that checkpoint blockade may have clinical efficacy for TSC and LAM, and possibly other benign tumor syndromes, potentially yielding complete and durable clinical responses.

Tsc2 disruption in mesenchymal progenitors results in tumors with vascular anomalies overexpressing Lgals3

Increased mTORC1 signaling from TSC1/TSC2 inactivation is found in cancer and causes tuberous sclerosis complex (TSC). The role of mesenchymal-derived cells in TSC tumorigenesis was investigated through disruption of Tsc2 in craniofacial and limb bud mesenchymal progenitors. Tsc2cKO^Prrx1-cre mice had shortened lifespans and extensive hamartomas containing abnormal tortuous, dilated vessels prominent in the forelimbs. Abnormalities were blocked by the mTORC1 inhibitor sirolimus. A Tsc2/mTORC1 expression signature identified in Tsc2-deficient fibroblasts was also increased in bladder cancers with TSC1/TSC2 mutations in the TCGA database. Signature component Lgals3 encoding galectin-3 was increased in Tsc2-deficient cells and serum of Tsc2cKO^Prrx1-cre mice. Galectin-3 was increased in TSC-related skin tumors, angiomyolipomas, and lymphangioleiomyomatosis with serum levels in patients with lymphangioleiomyomatosis correlating with impaired lung function and angiomyolipoma presence. Our results demonstrate Tsc2-deficient mesenchymal progenitors cause aberrant morphogenic signals, and identify an expression signature including Lgals3 relevant for human disease of TSC1/TSC2 inactivation and mTORC1 hyperactivity.

DOI:http://dx.doi.org/10.7554/eLife.23202.001

Tuberous sclerosis complex is a genetic condition that causes non-cancerous tumours with lots of blood vessels. It is caused by mutations that inactivate either of two genes known as TSC1 and TSC2. A signalling molecule called mTOR also contributes to the disease, and drugs that block its activity provide some relief for patients. However, mTOR regulates a wide variety of molecules and so researchers are looking for which ones are responsible for the formation of the tumours.

Mesenchymal cells produce bone, muscle and other structural tissues in the body. They also support the formation of blood vessels. Mice – which are often used as model animals in health research – also have mesenchymal cells and a gene that is very similar to the human TSC2 gene (known as Tsc2). Klover et al. hypothesized that disrupting the Tsc2 gene specifically in the mesenchymal cells of mice may mimic aspects of tuberous sclerosis complex in humans.

The experiments show that disrupting Tsc2 in mesenchymal cells does indeed mimic features of the human disease; the mice had shorter lifespans and they developed many tumours with dilated and winding blood vessels. Treating the mice with a drug that inhibits mTOR caused the tumours to shrink. Further experiments show that the loss of Tsc2 alters the production of many proteins involved metabolism, cell growth and sensing the levels of oxygen. For example, mouse cells that lack Tsc2 produce more of a protein called galectin-3, which appears to help blood vessels and tumours to grow in cancers.

Klover et al. also studied tumours from patients with tuberous sclerosis complex and a lung disease that is caused by mutations in TSC2 (called lymphangioleiomyomatosis). The experiments found that many tumours produce higher levels of galactin-3 than normal cells. Bladder cancers with mutations in TSC1 or TSC2 also had higher levels of galectin-3, suggesting that other diseases linked with mutations in these genes may also result in increased production of galectin-3.

The findings of Klover et al. suggest that galectin-3 may be a useful marker to assess the severity of tuberous sclerosis complex, lymphangioleiomyomatosis and to detect cancers with mutations in TSC1 or TSC2. The next step is to investigate whether galectin-3 alters blood vessels and tumour growth in these conditions.

DOI:http://dx.doi.org/10.7554/eLife.23202.002

Analysis of genotypes and phenotypes in Chinese children with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a neurocutaneous syndrome with serious clinical presentations, an autosomal dominant genetic disorder involving multiple organs and systems. We retrospectively investigated the clinical manifestations and genotypes of 20 Chinese children with TSC to enable informed diagnostic and surveillance recommendations in China. A retrospective analysis of clinical manifestations in 20 children (7.00±5.30 years old) with TSC was conducted. A genetic testing of the genes TSC1 and TSC2 was performed in 14 children.The earliest manifestations of TSC were skin lesions (80% of patients) and seizures (75%). Fourteen of the children presented with retinal hamartomas, and 2 of these underwent eye enucleation at other hospitals through misdiagnosis. On magnetic resonance imaging, 18 children exhibited subependymal nodules, and 16 ones showed cortical nodules. 5 cases of non-renal hamartomas, 5 cases of multiple renal cysts, and 5 cases of cardiac rhabdomyomas were observed. The genotyping of TSC1 and TSC2 in 14 children revealed 11 with mutations in TSC2, 2 with mutations in TSC1, and no mutations of either gene in one patient. Eight of these observed mutations are reported here in for the first time. The illness presentations of the TSC2-mutated patients were more severe than that of patients carrying TSC1 mutations.There were differences in the mutations of TSC genes in Chinese children from those reported in other countries. The described clinical characteristics and genotyping will help pediatric neurologists to understand, diagnosis, and treat TSC.

Epilepsy Mechanisms in Neurocutaneous Disorders: Tuberous Sclerosis Complex, Neurofibromatosis Type 1, and Sturge-Weber Syndrome

Neurocutaneous disorders are multisystem diseases affecting skin, brain, and other organs. Epilepsy is very common in the neurocutaneous disorders, affecting up to 90% of patients with tuberous sclerosis complex (TSC) and Sturge–Weber syndrome (SWS), for example. The mechanisms underlying the increased predisposition to brain hyperexcitability differ between disorders, yet some molecular pathways overlap. For instance, the mechanistic target of rapamycin (mTOR) signaling cascade plays a central role in seizures and epileptogenesis in numerous acquired and genetic disorders, including several neurocutaneous disorders. Potential routes for target-specific treatments are emerging as the genetic and molecular pathways involved in neurocutaneous disorders become increasingly understood. This review explores the clinical features and mechanisms of epilepsy in three common neurocutaneous disorders—TSC, neurofibromatosis type 1, and SWS.

Voltage-sensitive rhodol with enhanced two-photon brightness

We have designed, synthesized, and applied a rhodol-based chromophore to a molecular wire-based platform for voltage sensing to achieve fast, sensitive, and bright voltage sensing using two-photon (2P) illumination. Rhodol VoltageFluor-5 (RVF5) is a voltage-sensitive dye with improved 2P cross-section for use in thick tissue or brain samples. RVF5 features a dichlororhodol core with pyrrolidyl substitution at the nitrogen center. In mammalian cells under one-photon (1P) illumination, RVF5 demonstrates high voltage sensitivity (28% ΔF/F per 100 mV) and improved photostability relative to first-generation voltage sensors. This photostability enables multisite optical recordings from neurons lacking tuberous sclerosis complex 1, Tsc1, in a mouse model of genetic epilepsy. Using RVF5, we show that Tsc1 KO neurons exhibit increased activity relative to wild-type neurons and additionally show that the proportion of active neurons in the network increases with the loss of Tsc1. The high photostability and voltage sensitivity of RVF5 is recapitulated under 2P illumination. Finally, the ability to chemically tune the 2P absorption profile through the use of rhodol scaffolds affords the unique opportunity to image neuronal voltage changes in acutely prepared mouse brain slices using 2P illumination. Stimulation of the mouse hippocampus evoked spiking activity that was readily discerned with bath-applied RVF5, demonstrating the utility of RVF5 and molecular wire-based voltage sensors with 2P-optimized fluorophores for imaging voltage in intact brain tissue.

Combined Targeting of mTOR and Akt Using Rapamycin and MK-2206 in The Treatment of Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC), caused by loss-of-function mutations in the TSC1 or TSC2 genes, is an autosomal dominant disease characterized by benign tumor formation in multiple organs. Hyperactivation of mammalian target of rapamycin (mTOR) is the primary alteration underlying TSC tumor. Thus, rapamycin, as an mTOR specific inhibitor, has been assumed as a potential drug for the treatment of TSC. However, its application in TSC patients has been limited due to side effects. By analyzing Tsc1- or Tsc2-null mouse embryonic fibroblasts (MEFs), we found that loss of TSC1 or TSC2 led to a decreased sensitivity to MK-2206, a novel allosteric Akt inhibitor. Ectopic expression of a constitutively activated Akt (myristoylated Akt-1, myrAkt-1) sensitized Tsc2-null and Tsc1-null MEFs to MK-2206. Furthermore, MK-2206 increased the cytotoxicity of rapamycin in Tsc1^-/- or Tsc2^-/- MEFs. Moreover, the benefit of the combinatorial treatment was also demonstrated in a TSC xenograft mouse model. We conclude that the combination of rapamycin and MK-2206 may be utilized as a new therapeutic regimen for TSC.

Rare familial TSC2 gene mutation associated with atypical phenotype presentation of Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is a neurocutaneous disorder that results from mutations within either the TSC1 gene or the TSC2 gene. Diagnosis is based on well-established clinical criteria or genetic criteria. We describe an 18-month-old boy who presented with seizures and a single hypopigmented macule. He did not meet consensus criteria for the clinical diagnosis of TSC. Exome sequencing revealed a heterozygous TSC2 mutation (c.5138G>A (p.Arg1713His)) in the patient. This heterozygous alteration was detected in his mother as well as several other maternal family members. The mother and other family members with the mutation were asymptomatic except for the presence of hypopigmented macules. The phenotypic characteristics of the individuals in this family were not suggestive of a TSC2 mutation as none satisfied the clinical criteria for even a diagnosis of possible TSC. This case provides evidence for a unique TSC2 mutation that resulted in an atypical clinical presentation and indicates potential shortcomings of the current diagnostic criteria for TSC. These findings may have implications for genetic counseling and screening. © 2017 Wiley Periodicals, Inc.

Benign clear cell "sugar" tumor of the lung in a patient with Birt-Hogg-Dubé syndrome: a case report

Background

Birt-Hogg-Dubé (BHD) syndrome is a rare inherited autosomal genodermatosis and caused by germline mutation of the folliculin (FLCN) gene, a tumor suppressor gene of which protein product is involved in mechanistic target of rapamycin (mTOR) signaling pathway regulating cell growth and metabolism. Clinical manifestations in BHD syndrome is characterized by fibrofolliculomas of the skin, pulmonary cysts with or without spontaneous pneumothorax, and renal neoplasms. There has been no pulmonary neoplasm reported in BHD syndrome, although the condition is due to deleterious sequence variants in a tumor suppressor gene. Here we report, for the first time to our knowledge, a patient with BHD syndrome who was complicated with a clear cell “sugar” tumor (CCST) of the lung, a benign tumor belonging to perivascular epithelioid cell tumors (PEComas) with frequent causative relation to tuberous sclerosis complex 1 (TSC1) or 2 (TSC2) gene.

Case presentation

In a 38-year-old Asian woman, two well-circumscribed nodules in the left lung and multiple thin-walled, irregularly shaped cysts on the basal and medial area of the lungs were disclosed by chest roentgenogram and computer-assisted tomography (CT) during a preoperative survey for a bilateral faucial tonsillectomy. Analysis of the resected tumor showed large polygonal cells with clear cytoplasm proliferating in a solid pattern. Immunohistochemistry revealed that these tumor cells were positive for microphthalmia-transcription factor, S100, and CD1a but negative for HMB45, indicating that the tumor was a CCST. Genetic testing indicated that the patient had a germline mutation on exon 12 of the FLCN gene, i.e., insertion of 7 nucleotides (CCACCCT) (c.1347_1353dupCCACCCT). Direct sequencing of the FLCN exon 12 using genomic DNA obtained from her microdissected CCST cells clearly revealed loss of the wild-type FLCN sequence, which confirmed complete functional loss of the FLCN gene. On the other hand, no loss of heterozygosity around TCS1- or TSC2-associated genetic region was demonstrated.

Conclusion

To our knowledge, this is the first report of CCST of the lung in a patient with BHDS, indicating that CCST should be added to the spectrum of pulmonary manifestations of BHDS.

Rapamycin and rapalogs for tuberous sclerosis complex

BACKGROUND

Previous studies have shown potential benefits of rapamycin or rapalogs for treating people with tuberous sclerosis complex. Although everolimus (a rapalog) is currently approved by the FDA (U.S. Food and Drug Administration) and the EMA (European Medicines Agency) for tuberous sclerosis complex-associated renal angiomyolipoma and subependymal giant cell astrocytoma, applications for other manifestations of tuberous sclerosis complex have not yet been established. A systematic review is necessary to establish the clinical value of rapamycin or rapalogs for various manifestations in tuberous sclerosis complex.

OBJECTIVES

To determine the effectiveness of rapamycin or rapalogs in people with tuberous sclerosis complex for decreasing tumour size and other manifestations and to assess the safety of rapamycin or rapalogs in relation to their adverse effects.

SEARCH METHODS

Relevant studies were identified by authors from the Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE, and clinicaltrials.gov. Relevant resources were also searched by the authors, such as conference proceedings and abstract books of conferences, from e.g. the Tuberous Sclerosis Complex International Research Conferences, other tuberous sclerosis complex-related conferences and the Human Genome Meeting. We did not restrict the searches by language as long as English translations were available for non-English reports.Date of the last searches: 14 March 2016.

SELECTION CRITERIA

Randomized or quasi-randomized studies of rapamycin or rapalogs in people with tuberous sclerosis complex.

DATA COLLECTION AND ANALYSIS

Data were independently extracted by two authors using standard acquisition forms. The data collection was verified by one author. The risk of bias of each study was independently assessed by two authors and verified by one author.

MAIN RESULTS

Three placebo-controlled studies with a total of 263 participants (age range 0.8 to 61 years old, 122 males and 141 females, with variable lengths of study duration) were included in the review. We found high-quality evidence except for response to skin lesions which was judged to be low quality due to the risk of attrition bias. Overall, there are 175 participants in the treatment arm (rapamycin or everolimus) and 88 in the placebo arm. Participants all had tuberous sclerosis complex as proven by consensus diagnostic criteria as a minimum. The quality in the description of the study methods was mixed, although we assessed most domains as having a low risk of bias. Blinding of treatment arms was successfully carried out in all of the studies. However, two studies did not report allocation concealment. Two of the included studies were funded by Novartis Pharmaceuticals.Two studies (235 participants) used oral (systemic) administration of everolimus (rapalog). These studies reported response to tumour size in terms of the number of individuals with a reduction in the total volume of tumours to 50% or more relative to baseline. Significantly more participants in the treatment arm (two studies, 162 participants, high quality evidence) achieved a 50% reduction in renal angiomyolipoma size, risk ratio 24.69 (95% confidence interval 3.51 to 173.41) (P = 0.001). For the sub-ependymal giant cell astrocytoma, our analysis of one study (117 participants, high quality evidence) showed significantly more participants in the treatment arm achieved a 50% reduction in tumour size, risk ratio 27.85 (95% confidence interval 1.74 to 444.82) (P = 0.02). The proportion of participants who showed a skin response from the two included studies analysed was significantly increased in the treatment arms, risk ratio 5.78 (95% confidence interval 2.30 to 14.52) (P = 0.0002) (two studies, 224 participants, high quality evidence). In one study (117 participants), the median change of seizure frequency was -2.9 in 24 hours (95% confidence interval -4.0 to -1.0) in the treatment group versus -4.1 in 24 hour (95% confidence interval -10.9 to 5.8) in the placebo group. In one study, one out of 79 participants in the treatment group versus three of 39 in placebo group had increased blood creatinine levels, while the median percentage change of forced expiratory volume at one second in the treatment arm was -1% compared to -4% in the placebo arm. In one study (117 participants, high quality evidence), we found that those participants who received treatment had a similar risk of experiencing adverse events compared to those who did not, risk ratio 1.07 (95% confidence interval 0.96 - 1.20) (P = 0.24). However, as seen from two studies (235 participants, high quality evidence), the treatment itself led to significantly more adverse events resulting in withdrawal, interruption of treatment, or reduction in dose level, risk ratio 3.14 (95% confidence interval 1.82 to 5.42) (P < 0.0001).One study (28 participants) used topical (skin) administration of rapamycin. This study reported response to skin lesions in terms of participants' perception towards their skin appearance following the treatment. There was a tendency of an improvement in the participants' perception of their skin appearance, although not significant, risk ratio 1.81 (95% confidence interval 0.80 to 4.06, low quality evidence) (P = 0.15). This study reported that there were no serious adverse events related to the study product and there was no detectable systemic absorption of the rapamycin during the study period.

AUTHORS' CONCLUSIONS

We found evidence that oral everolimus significantly increased the proportion of people who achieved a 50% reduction in the size of sub-ependymal giant cell astrocytoma and renal angiomyolipoma. Although we were unable to ascertain the relationship between the reported adverse events and the treatment, participants who received treatment had a similar risk of experiencing adverse events as compared to those who did not receive treatment. Nevertheless, the treatment itself significantly increased the risk of having dose reduction, interruption or withdrawal. This supports ongoing clinical applications of oral everolimus for renal angiomyolipoma and subependymal giant cell astrocytoma. Although oral everolimus showed beneficial effect on skin lesions, topical rapamycin only showed a non-significant tendency of improvement. Efficacy on skin lesions should be further established in future research. The beneficial effects of rapamycin or rapalogs on tuberous sclerosis complex should be further studied on other manifestations of the condition.

Rapamycin requires AMPK activity and p27 expression for promoting autophagy-dependent Tsc2-null cell survival

Tuberous sclerosis complex (TSC) disease results from inactivation of the TSC1 or TSC2 gene, and is characterized by benign tumors in several organs. Because TSC tumorigenesis correlates with hyperactivation of mTORC1, current therapies focus on mTORC1 inhibition with rapamycin or its analogs. Rapamycin-induced tumor shrinkage has been reported, but tumor recurrence occurs on withdrawal from rapamycin. Autophagy has been associated with development of TSC tumors and with tumor cell survival during rapamycin treatment. mTORC1 and AMPK directly inhibit and activate autophagy, respectively. AMPK is hyperactivated in TSC cells and tumors, and drives cytoplasmic sequestration of the cell-cycle inhibitor p27KIP (p27). Whether AMPK and p27 are involved in rapamycin-induced autophagy and survival of TSC cells remain unexplored. Here, we show that inhibition of AMPK by compound C or by shRNA-mediated depletion of LKB1 reduces activation of autophagy by rapamycin in Tsc2-null cells. Similarly, shRNA-mediated depletion of p27 inhibited rapamycin-induced autophagy. In support of p27 lying downstream of AMPK on the activation of autophagy in Tsc2-null cells, a p27 mutant that preferentially localizes in the cytosol recovered the effect of rapamycin on autophagy in both p27- and LKB1-depleted cells, but a nuclear p27 mutant was inactive. Finally, we show that p27-dependent activation of autophagy is involved in Tsc2-null cell survival under rapamycin treatment. These results indicate that an AMPK/p27 axis is promoting a survival mechanism that could explain in part the relapse of TSC tumors treated with rapamycin, exposing new avenues for designing more efficient treatments for TSC patients.

A novel mouse model of tuberous sclerosis complex (TSC): eye-specific Tsc1-ablation disrupts visual-pathway development

Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome that is best characterised by neurodevelopmental deficits and the presence of benign tumours (called hamartomas) in affected organs. This multi-organ disorder results from inactivating point mutations in either the TSC1 or the TSC2 genes and consequent activation of the canonical mammalian target of rapamycin complex 1 signalling (mTORC1) pathway. Because lesions to the eye are central to TSC diagnosis, we report here the generation and characterisation of the first eye-specific TSC mouse model. We demonstrate that conditional ablation of Tsc1 in eye-committed progenitor cells leads to the accelerated differentiation and subsequent ectopic radial migration of retinal ganglion cells. This results in an increase in retinal ganglion cell apoptosis and consequent regionalised axonal loss within the optic nerve and topographical changes to the contra- and ipsilateral input within the dorsal lateral geniculate nucleus. Eyes from adult mice exhibit aberrant retinal architecture and display all the classic neuropathological hallmarks of TSC, including an increase in organ and cell size, ring heterotopias, hamartomas with retinal detachment, and lamination defects. Our results provide the first major insight into the molecular etiology of TSC within the developing eye and demonstrate a pivotal role for Tsc1 in regulating various aspects of visual-pathway development. Our novel mouse model therefore provides a valuable resource for future studies concerning the molecular mechanisms underlying TSC and also as a platform to evaluate new therapeutic approaches for the treatment of this multi-organ disorder.

Editors' choice: Conditional deletion of Tsc1 in the eye results in hamartoma formation and defects in retinal ganglion cell development – a novel mouse model providing insights into visual pathway involvement in TSC.

Papillary renal cell carcinoma: A review of the current therapeutic landscape

Renal cell carcinoma (RCC) is the most common cancer of the kidney and accounts for 2-3% of all adult malignancies. Clear cell carcinoma represents the most common histologic subtype, while papillary Renal Cell Carcinoma (pRCC) accounts for 10-20% of all renal cell cancers. While the inactivation of VHL gene can be found in the majority of clear cell carcinomas, different molecular mechanisms are involved into pRCC biology. Mutations in the MET oncogene are an essential step into the pathogenesis of hereditary pRCC forms, but they can be found only in a small rate of sporadic cases. Several agents, including anti-VEGF drugs and mTOR inhibitors, are possible options in the treatment of advanced and metastatic pRCC, following the demonstration of efficacy obtained in clinical trials including all RCC histologic subtypes. However, data specifically obtained in the subgroup of patients affected by pRCC are limited and not conclusive. Several ongoing trials are evaluating the efficacy of targeted therapy in papillary form. However, more rationale approaches based on molecular studies would help improving the outcome of these patients. Among others, MET inhibitors and targeted immunotherapy are promising new strategies for hereditary and sporadic disease. This review summarizes current knowledge on pRCC tumorigenesis and discusses recent and ongoing clinical trials with new therapeutic agents.

[Role of the mTOR pathway in the central regulation of energy balance]

The pathway of the mammalian (or mechanistic) target of rapamycin kinase (mTOR) responds to different signals such as nutrients and hormones and regulates many cellular functions as the synthesis of proteins and lipids, mitochondrial activity and the organization of the cytoskeleton. At the cellular level, mTOR forms two distinct complexes: mTORC1 and mTORC2. This review intends to summarize the various recent advances on the role of these two protein complexes in the central regulation of energy balance. mTORC1 activity modulates energy balance and metabolic responses by regulating the activity of neuronal populations, such as those located in the arcuate nucleus of the hypothalamus. Recent studies have shown that activity of the hypothalamic mTORC1 pathway varies according to cell and stimulus types, and that this signaling cascade regulates food intake and body weight in response to nutrients, such as leucine, and hormones like leptin, ghrelin and triiodothyronine. On the other hand, mTORC2 seems to be involved in the regulation of neuronal morphology and synaptic activity. However, its function in the central regulation of the energy balance is less known. Dysregulation of mTORC1 and mTORC2 is described in obesity and type 2 diabetes. Therefore, a better understanding of the molecular mechanisms involved in the regulation of energy balance by mTOR may lead to the identification of new therapeutic targets for the treatment of these metabolic pathologies.

The neural crest lineage as a driver of disease heterogeneity in Tuberous Sclerosis Complex and Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease, best characterized by the formation of proliferative nodules that express smooth muscle and melanocytic antigens within the lung parenchyma, leading to progressive destruction of lung tissue and function. The pathological basis of LAM is associated with Tuberous Sclerosis Complex (TSC), a multi-system disorder marked by low-grade tumors in the brain, kidneys, heart, eyes, lung and skin, arising from inherited or spontaneous germ-line mutations in either of the TSC1 or TSC2 genes. LAM can develop either in a patient with TSC (TSC-LAM) or spontaneously (S-LAM), and it is clear that the majority of LAM lesions of both forms are characterized by an inactivating mutation in either TSC1 or TSC2, as in TSC. Despite this genetic commonality, there is considerable heterogeneity in the tumor spectrum of TSC and LAM patients, the basis for which is currently unknown. There is extensive clinical evidence to suggest that the cell of origin for LAM, as well as many of the TSC-associated tumors, is a neural crest cell, a highly migratory cell type with extensive multi-lineage potential. Here we explore the hypothesis that the types of tumors that develop and the tissues that are affected in TSC and LAM are dictated by the developmental timing of TSC gene mutations, which determines the identities of the affected cell types and the size of downstream populations that acquire a mutation. We further discuss the evidence to support a neural crest origin for LAM and TSC tumors, and propose approaches for generating humanized models of TSC and LAM that will allow cell of origin theories to be experimentally tested. Identifying the cell of origin and developing appropriate humanized models is necessary to truly understand LAM and TSC pathology and to establish effective and long-lasting therapeutic approaches for these patients.

The analysis of mutations and exon deletions at TSC2 gene in angiomyolipomas associated with tuberous sclerosis complex

Angiomyolipomas (AMLs) are relatively rare hamartomatous or benign tumors that occasionally occur as part of tuberous sclerosis complex (TSC). Mutations in either of the two genes, TSC1 and TSC2, have been attributed to the development of TSC. Between 1994 and January 2009, 83 patients were diagnosed with AML at the Samsung Medical Center. In that group of patients, 5 (6%) had AML with TSC (AML-TSC). Mutational analysis of the TSC2 gene was performed using 7 samples from the 5 AML-TSC patients and 14 samples from 14 patients with sporadic AML without TSC (AML-non-TSC). From this analysis, mutations in TSC genes were identified in 5 samples from the AML-TSC patients (mutation detection rate=71%) and 3 samples from AML-non-TSC patients (mutation detection rate=21%). In the case of AML-TSC, 6 mutations were found including 3 recurrent mutations and 3 novel mutations, while in the case of AML-non-TSC, 4 mutations were identified once, including 1 novel mutation. Also MLPA analysis of the TSC2 gene showed that TSC2 exon deletion is more frequently observed in AML-TSC patients than in AML-non-TSC patients. This is the first mutation and multiplex ligation-dependent probe amplification (MLPA) analyses of TSC2 in Korean AMLs that focus on TSC. This study provides data that are representative of the distribution of mutations and exon deletions at TSC genes in clinically diagnosed AML-TSC cases of the Korean population.

The use of everolimus to target carcinogenic pathways in a patient with renal cell carcinoma and tuberous sclerosis complex: a case report

INTRODUCTION

An increased understanding of the genetic pathways involved in renal cell carcinoma has resulted in the development of various drugs that target relevant signaling cascades for the specific treatment of this disease. However, no validated predictive markers have been identified to guide the decision whether patients should receive vascular endothelial growth factor-targeted therapy or mammalian target of rapamycin-targeted therapy. We present what is, to the best of our knowledge, the first case of renal cell carcinoma in a patient with tuberous sclerosis complex who was successfully treated with everolimus.

CASE PRESENTATION

The patient was a 49-year-old Korean woman with tuberous sclerosis complex and recurrent renal cell carcinoma. The patient was treated with the tyrosine kinase inhibitor sunitinib followed by the mammalian target of rapamycin inhibitor everolimus. This treatment resulted in a prolonged response and significant clinical benefit. Notably, everolimus ameliorated the symptoms related not only to renal cell carcinoma but also to tuberous sclerosis complex.

CONCLUSION

This case provides a rationale for the use of everolimus as first-line treatment for this specific patient population in order to target the correct pathway involved in carcinogenesis.

TSC2 epigenetic defect in primary LAM cells. Evidence of an anchorage-independent survival

Tuberous sclerosis complex (TSC) is caused by mutations in TSC1 or TSC2 genes. Lymphangioleiomyomatosis (LAM) can be sporadic or associated with TSC and is characterized by widespread pulmonary proliferation of abnormal α-smooth muscle (ASM)-like cells. We investigated the features of ASM cells isolated from chylous thorax of a patient affected by LAM associated with TSC, named LAM/TSC cells, bearing a germline TSC2 mutation and an epigenetic defect causing the absence of tuberin. Proliferation of LAM/TSC cells is epidermal growth factor (EGF)-dependent and blockade of EGF receptor causes cell death as we previously showed in cells lacking tuberin. LAM/TSC cells spontaneously detach probably for the inactivation of the focal adhesion kinase (FAK)/Akt/mTOR pathway and display the ability to survive independently from adhesion. Non-adherent LAM/TSC cells show an extremely low proliferation rate consistent with tumour stem-cell characteristics. Moreover, LAM/TSC cells bear characteristics of stemness and secrete high amount of interleukin (IL)-6 and IL-8. Anti-EGF receptor antibodies and rapamycin affect proliferation and viability of non-adherent cells. In conclusion, the understanding of LAM/TSC cell features is important in the assessment of cell invasiveness in LAM and TSC and should provide a useful model to test therapeutic approaches aimed at controlling their migratory ability.

Co2/Erbium:YAG/Dye laser combination: an effective and successful treatment for angiofibromas in tuberous sclerosis

BACKGROUND

Tuberous sclerosis, an autosomal dominant neurocutaneous syndrome seen in approximately 1 in 6,000 people worldwide, is characterized by the appearance of hamartomas in multiple organs. The classic clinical triad consists of angiofibromas, epilepsy, and developmental delay. Dermatologic disorder is one of the main characteristics. Angiofibromas, a common form of presentation, causes significant cosmetic and medical problems. The current treatment for skin lesions is laser therapy. The carbon dioxide (CO2) laser has been used satisfactorily in treating these lesions, but several studies have demonstrated a high percentage of recurrences. Erbium:yttrium-aluminum-garnet (YAG) laser treatment has been used to resurface skin abnormalities in patients with dermatologic conditions. The dye laser as an alternative uses the principles of selective photothermolysis and is very effective in treating the vascular component of tuberous sclerosis. The use of all these lasers to treat skin lesions in patients affected by tuberous sclerosis has never been described in the literature.

METHODS

A retrospective study, conducted from 2007 to May 2013, investigated 13 patients who had tuberous sclerosis treated with an erbium:YAG/CO2/dye laser combination.

RESULTS

All the patients showed great improvement of their skin lesions. The results were evident immediately after the first treatment. No patient experienced complications or recurrence.

CONCLUSIONS

The combined use of the erbium:YAG/Dye/CO2 laser is a safe and effective treatment for skin lesions in patients affected by tuberous sclerosis.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Conditional deletion of Tsc1 in the female reproductive tract impedes normal oviductal and uterine function by enhancing mTORC1 signaling in mice

Heightened mammalian target of rapamycin complex 1 (mTORC1) activity by genetic deletion of its direct inhibitor, Tsc1, is associated with aberrant development and dysfunction of the female reproductive tract in mice. Here, we compared the phenotypes of mice with conditional deletion of Tsc1 in the female reproductive tract by either progesterone receptor (PR)-Cre (Tsc1(PR(d/d))), which inactivates Tsc1 in all major cell types in the uterus (epithelium, stroma and myometrium), or anti-Mullerian hormone type 2 receptor (Amhr2)-Cre (Tsc1(Amhr2(d/d))), which inactivates stromal and myometrial Tsc1. Tsc1(PR(d/d)) and Tsc1(Amhr2(d/d)) females are infertile resulting from oviductal hyperplasia, retention of embryos in the oviduct and implantation failure. In contrast to the appropriate embryonic development after fertilization seen in Tsc1(Amhr2(d/d)) females, embryo development was disrupted in Tsc1(PR(d/d)) females. In addition, uteri in Tsc1(PR(d/d)) and Tsc1(Amhr2(d/d)) females showed epithelial hyperplasia but not endometrial cancer. In conclusion, Tsc1(PR(d/d)) and Tsc1(Amhr2(d/d)) have overlapping yet distinct phenotypes in the context of compartment-specific deletion of Tsc1.

Progressive development of polycystic kidney disease in the mouse model expressing Pkd1 extracellular domain

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by slow progression of multiple cysts in both kidneys that lead to renal insufficiency in mid-life or later. ADPKD is associated with mutations mainly in the PKD1 gene (encoding polycystin-1 or PC1) and less frequently in the PKD2 gene (encoding polycystin-2 or PC2). To mimic naturally occurring human PKD1 mutations and gain insight into the PC1 extracellular domain function, four transgenic mouse lines were established with exclusively the extracellular domain of the Pkd1 gene (Pkd1(extra)) under endogenous transcriptional regulation. Expression of the Pkd1(extra) transgene was 2- to 80-fold above endogenous levels. Strikingly, the Pc1(extra) protein was more abundant, proportionally to the endogenous levels. All four transgenic mouse lines consistently displayed progressive renal cystic phenotype. Consequently, these transgenic mice reproducibly developed renal functional alterations similar to human ADPKD with proteinuria, renal insufficiency, anemia and died of renal failure late in life. In precystic kidneys, the Pkd1(extra) transgene modulated Pc2 expression and thereby, uncovered a potential Pc1-mutant/Pc2 pathogenic crosstalk mechanism. Moreover, the pathophysiologic mechanism also implicates c-myc, a major modulator of cystogenesis. Altogether, the novel Pkd1(extra) mouse model is the first Pc1 extracellular mutant that reproduces human ADPKD clinical progression and physiopathology.

Hypoxia-inducible factor 1a is a Tsc1-regulated survival factor in newborn neurons in tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a genetic disorder caused by mutations in TSC1 or TSC2 resulting in hyperactivity of the mammalian target of rapamycin and disabling brain lesions. These lesions contain misplaced neurons enriched in hypoxia-inducible factor 1a (HIF1a). However, the relationship between TSC1/2 and HIF1a and the function of HIF1a in TSC neurons remain unexplored. Here, we examine the degree of HIF1a activity and its function in newborn Tsc1(null) neurons in a mouse model of TSC. Using single cell electroporation in the neurogenic subventricular zone (SVZ) of neonatal mice, we deleted Tsc1 and generated olfactory lesions containing misplaced Tsc1(null) neurons as previously reported. These newborn neurons displayed elevated HIF1a-mediated transcriptional activity when compared with Tsc1 heterozygote neurons and a marked resistance to cell death induced by a HIF1a antagonist. Electroporation of Hif1a targeting short hairpin RNA (shRNA) or dominant negative HIF1a constructs resulted in 80-90% loss of Tsc1(null) newborn neurons although sparing SVZ stem cells. Consistent with this later finding, induction of Hif1a shRNA expression during synaptic integration thus bypassing neuron production also resulted in newborn neuron death. Collectively, these results suggest that HIF1a acts as a molecular determinant of newborn neuron survival and that its TSC1-dependent up-regulation gave Tsc1(null) neurons a survival advantage, despite their misplacement in a novel microenvironment.

Renal angiomyolipomas in tuberous sclerosis--rare but potentially life-threatening lesions

We discuss an 18-year-old girl, diagnosed with tuberous sclerosis complex and known to have renal angiomyolipomas (AMLs) but having no regular urological follow-up, who presented with left-sided abdominal pain and haematuria on urine dipstick testing at the out-of-hours General Practitioner (GP) service. She was diagnosed as having urinary tract infection/pyelonephritis and discharged with simple analgesia and antibiotics. Subsequent imaging of her renal tract demonstrated multiple large AMLs with evidence of recent bleeding, which required arterial embolisation.

The search for allelic variants that cause monogenic disorders or predispose to common, complex polygenic phenotypes

The search for the mutant genes for monogenic disorders has been a spectacular success. This was accomplished because of the mapping and sequencing of the human genome, the determination of the sequence variability, the collection of well-characterized families with mendelian disorders, the development of statistical methods for linkage analysis, and laboratory methods for mutation search. The challenge of the genetic medicine is now to decipher the nucleotide sequence variants that predispose to common complex, polygenic phenotypes. The methodology for this challenge is in development and constant evolution, it is anticipated that, in the next 10 to 20 years, susceptibility alleles for these common disorders will be identified.

Giant angiofibromas in tuberous sclerosis complex: a possible role for localized lymphedema in their pathogenesis

BACKGROUND

Giant angiofibromas in patients with tuberous sclerosis complex (TSC) are rare.

OBJECTIVE

We sought to report two patients who had TSC with unusually large and disfiguring facial angiofibromas and to identify underlying histopathologic changes that may possibly explain the clinical features.

METHODS

We performed a clinicopathologic, immunohistochemical, and molecular biologic study using 42 lesional specimens and peripheral blood from one of the two patients. The immunohistochemical investigations were mainly focused on the vascular moiety of the lesions. TSC1 and TSC2 alterations were studied using multiplex ligation-dependent probe amplification for large deletion/duplication mutations, whereas screening for small mutations was performed using polymerase chain reaction amplification of individual coding exons and exon-intron junctions of both genes followed by an analysis on denaturation gradient gel electrophoresis.

RESULTS

Histopathologic examination revealed, in addition to findings typical of angiofibroma, several unusual features including multinucleated giant cells containing multiple intracytoplasmic vacuoles, Touton-like cells, emperipolesis, pagetoid dyskeratosis, vacuolar alteration at the dermoepidermal junction, Civatte bodies, and melanophages in the subjacent dermis. Numerous dilated lymphatic vessels were detected indicating localized lymphostasis, probably caused by secondary lymphedema. The lymphatic nature of the vessels was confirmed by immunohistochemical study. Genetic testing for TSC1 and TSC2 gene mutations revealed a substitution on position c.2251C>T resulting in a nonsense mutation R751X in fragment 20.2.

LIMITATIONS

Histopathologic specimens and peripheral blood were available from only one patient.

CONCLUSION

Localized lymphedema may contribute to the formation of large disfiguring angiofibromas in patients with TSC.